Methods and devices for embolic protection

ABSTRACT

An aortic flow diverter or filter is described that diverts particles away from the carotid vessels and right subclavian artery. The diverter includes a stent-like portion formed from a plurality of braided or woven wires that can radially self-expand. The stent-like portion is generally tubular and is fixed over the distal end of a catheter or shaft. A sheath is located over both the catheter and stent-like portion, maintaining the stent-like portion in a compressed configuration. When withdrawn proximally, the sheath releases the stent-like portion, allowing it to expand against the walls of the vessel.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/833,223 filed Jun. 10, 2013 entitled Methods and Devices forEmbolic Protection, which is hereby incorporated herein by reference inits entirety.

BACKGROUND

As the world population continues to age, cardiovascular procedures willgrow in frequency and complexity. In order to improve the safety andefficacy of such procedures, the complication of embolism associatedwith those procedures must be addressed.

An embolism is when thrombus or atheroma or calcium breaks loose from apatient's vasculature during a procedure and migrates distally andlodges in a peripheral vessel causing ischemic injury to the end organ.

A particularly acute complication is a cerebral embolism where an embolilodges in one of the arteries of the brain and thus causes an injury tothe brain. Accordingly, in a preferred embodiment, the invention focusesprimarily on cerebral protection during heart operations such ascoronary artery bypass surgery (CABG) and valve replacement, the latterbeing performed either by open chest surgery or through percutaneousdelivery, e.g., trans-catheter aortic valve replacement (TAVR).

Traditional cerebral protection during open or closed heart procedureshas involved administration of blood thinners (e.g. anticoagulants).However, this approach is directed more to the risk that arises due tothe bleeding caused by surgical incisions. Such blood thinners do notaddress complications where the embolism is not responsive toanticoagulation.

Other methods include the use of aortic cannulas which have filtersincorporated (e.g., Embolex) in the aorta as a way of protecting thebrain. However, the large size and rigidity of these cannulas make themsomewhat cumbersome.

More recently, in connection with TAVR procedures, surgeons have useddiverters or filtration devices such as CLARET and EMBRELLA. Informationregarding these devices are described and explained in the followingreferences:

-   -   1. “Embolic Protection during TAVI Embrella,” Nikos Werner,        Universitätsklinikum Bonn, Bonn, Germany, CS Frankfurt 2012.    -   2. “Brain Damage—Will Embolic Protection Devices Reduce Strokes        After TAVR?”, Andreas Baumback, MD, FRCP, FESC, Bristol Heart        Institute, University Hospitals Bristol, ICI 2012.    -   3. “CardioLogical Receives Patent for Aortic Embolic Protection        Devices to Prevent During TAVR,” Diagnostic and Interventional        Cardiology, Apr. 12, 2013,        www.dicardiology.com/article/cardiological-receives-patent-aortic-embolic-protection-devices-prevent-during-tavr,        accessed Apr. 28, 2013.    -   4. “Emboline,” www.emboline.com/technology.html, accessed Apr.        28, 2013.    -   5. “Intraprocedural Intraaortic Embolic Protection With the        EmboIX Device in Patients Undergoing Transaortic Transcatheter        Aortic Valve Implantation (TAo-EmboIX),” ClinicalTrials.gov,        clinicaltrials.gov/ct2/show/NCT01735513, accessed Apr. 28, 2013.    -   6. “Embolic Protection Devices for TAVR Show Promise,” TCTMD,        The source for Interventional Cardiovascular News and Education,        www.tctmd.com/show.aspx?id=110221&AspxAutoDetectCookieSupport=1,        accessed Apr. 28, 2013.

These devices can essentially be divided into two categories: 1. Flowdiverters where the emboli are diverted from entering vessels, e.g., thecerebral vessels; and, 2. Filtration devices where the emboli arecaptured and removed from the blood stream entirely.

The reliability and effectiveness of these devices is yet to be reliablyverified. The need for some type of embolism protection, however,remains essential. Accordingly, there is an ongoing need for thedevelopment of systems and methods of protecting patients from embolithat are safe and effective. Accordingly, it is an object of the presentinvention to provide a system and method of more effectively providingprotection from embolism to a patient during surgical procedures, andparticularly protection from cerebral embolism.

SUMMARY OF THE INVENTION

One embodiment of the present invention is directed to an aortic flowdiverter or filter that diverts particles away from the carotid vesselsand right subclavian artery. Preferably, the diverter includes astent-like portion formed from a plurality of braided or woven wiresthat can radially self-expand. The stent-like portion is generallytubular and is fixed over the distal end of a catheter or shaft. Asheath is located over both the catheter and stent-like portion,maintaining the stent-like portion in a compressed configuration. Whenwithdrawn proximally, the sheath releases the stent-like portion,allowing it to expand against the walls of the vessel.

In one embodiment, the filter is positioned through the right subclavianartery, over the opening of the right common carotid artery and into theleft common carotid artery. The sheath is withdrawn, allowing thestent-like portion to expand. A trans-catheter aortic valve replacement(or other similar procedure) is performed to repair or replace an aorticvalve. Once the valve procedure is complete, the sheath is advanced overthe stent-like portion and the filter is removed from the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments ofthe invention are capable of will be apparent and elucidated from thefollowing description of embodiments of the present invention, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a rendering of one preferred embodiment of an aortic flowdiverter (AFD) in accordance with the present invention shown being usedduring a TAVR procedure;

FIGS. 2A-2F are renderings of the various steps of deploying andretrieving an aortic flow diverter in accordance with one preferredembodiment of the present invention;

FIGS. 3A-3B are renderings of preferred embodiments of the working endof an aortic flow diverter in accordance with the present invention;

FIG. 4 is a rendering of a preferred embodiment of the back end of anaortic flow diverter in accordance with the present invention;

FIG. 5 is a rendering of a preferred embodiment of an aortic flowdiverter in accordance with the present invention shown being usedduring a TAVR procedure; and,

FIGS. 6A and 6B is a rendering of a preferred embodiment of an aorticflow diverter.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

In accordance with one embodiment of the present invention, a dual layerself-expanding Nitinol frame stent-like device is used as a flowdiverter during cardiovascular procedures to prevent cerebral embolism.

Such a stent-like device used in the manner herein disclosed reduces theembolic load to the brain by effectively diverting the particles awayfrom the carotid vessels and right subclavian artery. One reason thatsuch effectiveness is obtained is because the device achieves superiorwall apposition.

Moreover, using a stent-like device (or other similarly configureddevice) in this manner is low profile and thus avoids taking up space inthe femoral artery (which must remain open for TAVR devices 50) andavoids the aortic arch 16. Hence, the device and technique substantially(if not completely) avoids impeding the valve replacement procedure.

Referring to FIG. 1, an aortic flow diverter 100 having a double layerNitinol retrievable self-expanding stent-like portion 104 is shown inits deployed state extending from the right subclavian artery 10, overthe opening of the right common carotid artery 12 and into the leftcommon carotid artery 14. This deployment is shown in the context of aTAVR procedure TAVR catheter 50. However, the aortic flow diverter 100can be used in any type of heart procedure including more traditionalaortic valve replacement (AVR) procedures.

Due to the flexibility and expandability of the woven/braided stent-likeportion 104 of the diverter 100, superior apposition of the diverterframe against the inner walls of the vessels is achieved. This ensuresthat a minimum number and minimum size of emboli are allowed into thecerebral arteries. Hence, the braiding and/or mesh characteristics ofthe woven/braided stent-like portion 104 of the diverter 100 divert suchemboli away from the cerebral arteries.

In a preferred embodiment the woven/braided stent-like portion 104 ofthe diverter 100 is a tubular, dual-layer, self-expanding, Nitinol framestent-like member made by Microvention, Inc. under the name CASPER. Arepresentation of this stent can be found in U.S. Publication No.2012/0310319 entitled Stent, published Dec. 6, 2012, which is hereinincorporated by reference in its entirety.

Referring to FIGS. 2A-2F, one embodiment of a method for deploying andretrieving an aortic flow diverter 100 in accordance with the presentinvention is disclosed.

Referring to FIG. 2A, a guidewire 102 is directed from the RSCA 10 tothe LCCA 14 of the patient. In a preferred embodiment the guidewire 102is a stiff 0.035″ Amplatz guidewire. A catheter 104 (e.g., a Simmons 2catheter) is then delivered over the guidewire 102.

Referring to FIG. 2B, a sheath 106 (e.g. 6F in size) containing theaortic flow diverter 100 compressed on a catheter shaft 108 of adelivery catheter 108 (shown in FIGS. 3A and 3B) is then placed over theguidewire 102. The sheath 106 and catheter 108 are advanced over theguidewire, through the RSCA 10 to the LCCA 14 of the patient. In apreferred embodiment, the sheath 106 is a 6F Cook sheath or 6F TerumoPinnacle sheath.

Referring to FIG. 2C, deployment of the aortic flow diverter 100 isinitiated by withdrawing the sheath 106 to expose the tubular,stent-like portion 104 on the catheter shaft 120, after purging thesystem of any air bubbles.

Referring to FIG. 2D, further deployment of the diverter 100 is shown asthe sheath 106 continues to be retracted. As the stent-like portion 104is exposed, it self-expands radially against the walls of the vessels.Also shown are the initial steps of a TAVR procedure where a TAVRcatheter 50 is advanced through the femoral artery and into the aorta11.

Referring to FIG. 2E, full deployment of the stent-like portion 104 ofthe diverter 100 is depicted, as the sheath 106 is retracted into theRSCA 10. Due to the wall apposition of the stent-like portion 104, anyemboli resulting from the TAVR procedure are diverted away from thecerebral arteries.

Referring to FIG. 2F, the diverter 100 is retrieved by advancing thesheath 106 in a distal direction and thereby causing the stent-likeportion 104 to be contracted inwardly on to the catheter shaft 120. Oncethe stent-like portion 104 is fully captured in the sheath 106, theentire apparatus (i.e., the sheath 106, catheter 108, diverter 100, andguidewire 102) is removed from the patient.

Referring to FIG. 3A, the distal working end of the diverter 100,catheter 108, and sheath 106 in the closed position is shown. As can beseen, the sheath fully captures the stent-like portion 104 of thediverter 100. A nose cone 114 at the distal end of the catheter shaft120 allows smooth advancement of the device into the carotid vessels. Inorder to ensure proper placement of the diverter 100, radiopaque markers112 are disposed on the proximal and/or distal ends of the stent portionof the stent-like portion 104. Additionally, the sheath 106 may includea monorail opening 106A near its distal end for over-the-wire use.

Referring to FIG. 3B, the working end of the diverter 100 in the openposition is shown. As can be seen, the sheath 106 has been withdrawnproximally, thus allowing the stent-like portion 104 to expand. Thenosecone 114 is separated from the distal end of the stent-like portion104 of the diverter 100 by the radial expansion of the stent-likeportion 104 peeling away from the shaft 120. The proximal portion of thestent-like portion 104, however, remains fused (e.g., by an adhesive,metal band, or welding) at point 104A on the shaft 120, preventing itfrom opening and allowing the stent-like portion 104 to be easilyretrieved.

Preferably, the stent-like portion is woven or braided with at least twodifferent diameter wires. For example, larger diameter wires 156 (e.g.,0.002-0.004 inches) can form a more rigid framework while smallerdiameter wires 158 (e.g., 0.0010-0.0020 inches) can be woven to form arelatively small pour size (e.g. 150-200 microns). Preferably, both ofthese wires are made from Nitinol and are electropolished. These wires156 and 158 can be woven into a single layer or the larger diameterwires 156 can be woven into an outer layer and the smaller diameterwires can be woven into an inner layer that is physically connected tothe outer layer at various locations.

Referring to FIG. 4, the back end of the sheath 106 is connected with atraditional Touhey Borst adapter 122. The shaft 120 and stent-likeportion 104 are movable in and out of the adapter 122 over the guidewire 102 into and out of the vessels as needed.

Referring to FIGS. 5, 6A, and 6B, another embodiment of a diverter 150is shown wherein the stent-like portion 152 has a tapered and/or closeddistal end 154A just below the nosecone with which it is fused toprovide distal filtration. The proximal end is similar to that shown inFIG. 4, in which the sheath 106 is connected to a Touhey Borst via a hub115. Additionally, the inner shaft 120 may include a handle 123.

In one embodiment, the pore size or cell size of the outer layer of thedual layer stent be 200-250 microns. This pore/cell size together withthe radial expansion characteristics of inner frame/layer of the duallayer stent provides both the radial strength needed to give radialconformity and yet is still deliverable as well as maximize flowdiversion. Small pore size reduces the particles that enter the stentand cerebral vessels during the filtration process.

In a preferred embodiment, e.g., see FIG. 5, the distal end of an outerlayer of the dual layer stent is closed just beyond the inner layer.This configuration provides supplemental filtration of the left carotidartery and traps any material that enters the first layer of the duallayer stent. In another embodiment, the distal end of the outer layerremains open while the distal end of the inner layer is closed.

In another embodiment, the distal end of the stent-like portion caninclude a plurality of anchors to help maintain its position within theleft common carotid artery. For example, such anchors could include aplurality of spikes, hooks, coils, or similar structures that areradially disposed on an outer surface of the stent-like portion.

In another embodiment, the stent-like portion has a length between 3-12inches.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

What is claimed is:
 1. A method of protecting a patient from embolismduring a surgical procedure comprising: directing a delivery catheterthrough the right subclavian artery of a patient to a left commoncarotid artery of the patient; deploying a stent-like device in saidleft common carotid artery and said right subclavian artery from saiddelivery catheter such that apposition of said stent-like device issubstantially achieved on the walls of said left common carotid arteryand said right subclavian artery; said stent-like device having anouter, tubular layer woven from wires having a diameter within a rangeof about 0.002 to 0.004 inch, and an inner, tubular layer woven fromwires within a range of about 0.0010 to 0.0020 inch; said outer, tubularlayer being disposed over said inner, tubular layer and being physicallyconnected to said inner layer at a plurality of locations; said innertubular layer and said outer tubular layer both having substantially thesame length within a range of 3-12 inches; said inner tubular layerbeing open at its distal end and a distal end of said outer tubularlayer being closed to form a cone shape distally beyond said innerlayer; performing a valve replacement procedure; retrieving saidstent-like device.
 2. The method of claim 1, wherein said deploying saidstent-like device further comprises proximally retracting a sheath andallowing radial expansion of said stent-like device.
 3. The method ofclaim 1, wherein a proximal end of said stent-like device is fixed to ashaft positioned through said stent-like device.
 4. The method of claim3, wherein a distal end of said stent-like device is fixed to a shaftpositioned through said stent-like device.
 5. The method of claim 1,wherein said deploying said stent-like device is followed by divertingpassage of emboli into said right subclavian artery and said left commoncarotid artery with said stent-like device.
 6. The method of claim 1,wherein said deploying said stent-like device is followed by capturingemboli from blood passing into said right subclavian artery and saidleft common carotid artery with said stent-like device.
 7. The method ofclaim 1, further comprising a plurality of anchor members radiallydisposed on said outer tubular layer.
 8. The method of claim 1, whereinsaid inner tubular layer forms a pore size between 150 to 200 microns,and said outer tubular layer forms a pore size between 200 to 250microns.
 9. A method of protecting a patient from embolism during asurgical procedure comprising: advancing a delivery catheter systemthrough the right subclavian artery of a patient to a left commoncarotid artery of the patient; proximally retracting a tubular sheath toexpose a stent-like device located on a distal end of an inner cathetershaft, so as to allow said stent-like device to radially expand from afirst compressed diameter to a second expanded diameter; said stent-likedevice having an outer, tubular layer woven from wires having a diameterwithin a range of about 0.002 to 0.004 inch, and an inner, tubular layerwoven from wires within a range of about 0.0010 to 0.0020 inch; saidouter, tubular layer being positioned over said inner, tubular layer andphysically connected to said inner layer at a plurality of locations;said inner tubular layer and said outer tubular layer both havingsubstantially the same length within a range of 3-12 inches; said outertubular layer being open at its distal end and a distal end of saidinner tubular layer being closed to form a cone shape; continuing toproximally retract said tubular sheath until said stent-like device isexposed and in said second expanded diameter between said left commoncarotid artery and said right subclavian artery; performing an aorticvalve replacement procedure; distally advancing said sheath over saidstent-like device so as to contract said stent-like device from saidsecond expanded diameter to said first compressed diameter.